The amount of data transferred between electronic devices has grown tremendously the last few years. Large amounts of audio, video, text, and other types of data content are now regularly transferred among computers, media devices, such as handheld media devices, displays, storage devices, and other types of electronic devices. Since it is often desirable to transfer this data rapidly, the data rates of these data transfers have substantially increased.
Transferring data at these rates has proven to require a new type of cable. Conventional, passive cables create excessive skew between high-speed signals and generate large amounts of electromagnetic emissions that degrade signal quality. Because of this, active cables are being developed to support the high data rates among these electronic devices. These active cables may include electronic circuits that receive, retime, and retransmit data to and from a far end of the cable. These circuits receive and provide signals on connector contacts, which are typically located in connector inserts at each end of the cable.
But these high speed cables are susceptible to damage. For example, static charge can build up on a user of these cables. The user may touch one or more contacts at a cable's connector. This in turn may cause a discharge of the static that has built up on the user, resulting in a transfer of charge from the user to the connector contact. This discharge of static is commonly referred to as electrostatic discharge (ESD). Without proper protection, this discharge can cause excessive voltages to appear at the electronic circuits located in these new, high-speed cables.
Traditionally, ESD protection involves the use of diodes or other junctions that conduct the discharge current safely to ground. Unfortunately, these diodes and other junctions add capacitance to the signal lines that are being protected. These capacitances slow signal edges and degrade high-speed performance.
Thus, what is needed are circuits, methods, apparatus, and other structures that can provide low-capacitance protection from electrostatic discharges at cable connector contacts, as well as other applications.